GB2045182A

GB2045182A - Steering arrangement for a vehicle

Info

Publication number: GB2045182A
Application number: GB8002672A
Authority: GB
Original assignee: O&K Orenstein and Koppel GmbH
Current assignee: CNH Industrial Baumaschinen GmbH
Priority date: 1979-01-26
Filing date: 1980-01-25
Publication date: 1980-10-29
Also published as: SE8000587L; NL8000147A; CA1145680A; US4394886A; IT1145429B; IT8047618A0; JPS55102779A; GB2045182B; BR8000486A

Description

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GB 2 045182 A

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SPECIFICATION

Steering arrangement for a vehicle

5 The invention relates to a steering arrangement for a vehicle, in particular a vehicle that has, according to choice, either hydraulically-assisted mechanical steering or purely hydraulic steering.

In a steering arrangement of this type, the conver-10 sion from hydraulically-assisted steering into purely hydraulic steering is, conventionally, effected by means of the selective connection of a propeller shaft, which is connected to the steering wheel, of the vehicle, to one of the two systems used for 15 operating the steering. The purely hydraulic steering may be required to provide, not only for front axle steering, but also for the front and rear axles both being steered, either in opposite directions (when a minimal degree of lock is required) or in the same 20 direction. To this end, it is known to provide two hydraulic pumps and two hydraulic circuits for operating the hydraulically-assisted and purely hydraulic steering systems, as well as a double steering device but such an arrangement has been found to 25 be expensive and susceptible to failure.

British Patent Applicaton No. 40231/78 (Serial No. 2010197) describes a steering arrangement comprising an hydraulic circuit including an hydraulic pump selectively connectible to supply fluid to first and 30 second steering valve means. The first steering valve means is used when the vehicle is being mechanically steered with hydraulic assistance, and the second steering valve means is used when the vehicle is being steered purely hydraulically. The second steer-35 ing valve means controls the supply of fluid from the pump to hydraulic cylinders of the front and rear axles of the vehicle to steer either the front axle only, or the front and rear axles together (either in the same or in opposite directions).

40 A possible drawback of the steering arrangement described in Application No. 40231/78 Serial No. 2010197 becomes evident when the vehicle is moving and the driver wishes to steer while being able to see across the rear axle (as is the case, for example, 45 if the driver's cab has swung through 180° or if an upper chassis carrying a fixed crane cab has swung i.e. when the rear axle is disposed forwardly in the direction of travel). In these circumstances, the driver must take care when he turns the steering 50 wheel because the turning circle of the wheels on the rear axle is opposite to the rotaton of the steering wheel, so that when the steering wheel is turned to the left, the vehicle makes a right-hand turn, and vice versa. This unaccustomed reaction of the vehicle to 55 the operation of the steering wheel requires great concentraton on the part of the operator, and there arises the danger that accidents and damage may occur as a result of an incorrect reaction by the operator when the vehicle strikes obstacles. 60 The present invention provides a steering arrangement for a vehicle, comprising an hydraulic circuit including an hydraulic pump selectively connectible to supply fluid to first and second steering valve means, the first steering valve means being operable 65 to control the supply of fluid from the pump to an hydraulic cylinder for one axle of the vehicle to assist mechanical steering of the vehicle, and the second steering valve means being operable to control the supply of fluid from the pump to hydraulic cylinders 70 of two axles of the vehicle to steer those axles, the second steering valve being selectively connectible to control the supply of fluid to the hydraulic cylinders at least to steer either of those axles alone.

In an embodiment of the invention, the hydraulic 75 pump, acting on both the hydraulically-assisted and purely hydraulic steering systems and driven by a drive motor, is connected, via a line, a current-regulating and pressure relief valve and a line, to a first spool valve from which:

80 (i) on the one hand, a line leads to the first steering valve means comprising a steering gear operated by the steering device of the vehicle via a propeller shaft, from which steering gear lines lead to a second spool valve that is connected via lines to 85 the hydraulic cylinders of the front axle of the vehicle and

(ii) on the other hand, a line leads to the second steering valve means comprising a steering valve • that is operated by means of the steering device and 90 the propeller shaft, pressure oil flowing from the steering valve either

(a) via a line to a third spool valve and via a line to the hydraulic cylinders of the front axle or

(b) via a line to a fourth spool valve and via a line, 95 the third spool valve and a line to the hydraulic cylinders of the front axle or

(c) via a line to the third spool valve and via a line to the hydraulic cylinders of the front axle as well as via a line to the third spool valve and via a line, to the

100 fourth spool valve and a line to the hydraulic cylinders of the rear axle or

(d) via a line to the fourth spool valve and via a line to the hydraulic cylinders of the rear axle as well as via a line to the fourth spool valve and via a line,

105 the third spool valve and a line to the hydraulic cylinders of the front axle or

(e) via a line to the third spool valve and, via a line, the fourth spool valve and a line to the hydraulic cylinders of the rear axle only or

110 (f) via a line to the fourth spool valve and via a line to the hydraulic cylinders of the rear axle only.

An embodiment of the invention will now be described by way of example, with reference to the accompanying drawing, in which:

115 Figure 1 shows a hydraulic circuit diagram of a steering arrangement, and

Figure 2 shows the front and rear axles of a vehicle steered with the arrangement according to Figure 1.

In the circuit shown in Figure 1, pressure oil flows 120 from a hydraulic pump 10, which is driven by a motor 11, via a line 12, a current regulating and pressure relief valve 49 and a line 50 to a spool valve 13. When the valve 13 is in the position "a" shown in the drawing, the oil flows from there via a line 14 to 125 steering gear 15 which is operated by means of the steering wheel 16 of the vehicle, via steering column 17, V-drive 18 and propeller shaft 19. Lines 20 and 21 lead from the steering gear 15 to a spool valve 22 which is connected via lines 23 and 24 and lines 46 130 and 47 to the hydraulic cylinders 25 and 26 of the

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GB 2045182 A

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vehicle front axle 41 (Figure 2).

When the spool valve 13 is in the alternative position "b", the pressure oil fed by the hydraulic pump TO flows through a line 27 (instead of the line 5 14) to a steering valve 28 which can also be operated by the steering wheel 16 when the propeller shaft 19 has been released from the connection to the steering gear 15 and connected instead to the steering valve 28 as indicated in dotted lines. 10 Assuming that front axle steering only is required and depending on the position of the steering val ve 28, pressure oil is fed from the steering valve either:

(i) via a line 29 to a spool vafve30 (which, as described below, is now in position "b") and then via

15 the line 46 to the hydraulic cylinders 25 and 26 of the front axle 41 or

(ii) via a line 31 to a spool valve 32 (in the position "a" shown in the drawing) and then via a line 33, the spool valve 30 (still in position "b") and the

20 line 47 to the hydraulic cylinders 25 and 26 of the front axle 41.

When, on the other hand, rear axle steering is connected in addition to front axle steering (and depending, again, on the position of the steering 25 valve 28) pressure oil is fed from the steering valve either

(iii) via the line 29 to the spool valve 30 (still in position "b") and then via the line 46 to the hydraufic cylinders 25 and 26 ofthefrontaxle41 as well as

30 from the hydraulic cylinders 25,26 via the line 47, the spool valve 30, the line 33, the spool valve 32 (either in position "b" or"c") and, depending on the position of the spool valve 32, a line 34 or 35 to the hydraulic cylinders 36 and 37 of the vehicle rear axle 42 (Figure 35 2) or

(iv) via the line 31, the spool valve 32 (again, either in position "b"or"c") and, depending on the position of the spool valve 32 the line 34 or 35 to the hydraulic cylinders 36 and 37 of the rear axle 42 as

40 well as from the hydraulic cylinders 36,37 via the line 35 or 34 to the spoof valve 32, via the Tine 33, the spool valve 30 (still in position "b") and the line 47 to the hydraulic cylinders 25 and 26 of the front axle 41.

If, however, rear axle steering only is required, 45 pressure oil is fed from the steering valve 28 either:

(v) via the line 29 to the spool valve 30 (which, as described below, is now in position "a") and then via line 33, the spool valve 32 (now in position "b") and the line 34 to the hydraulic cylinders 36 and 37 of the

50 rear axle 42 or

(vi) via the line 31 to the valve 32 (still in position "b") and then via line 35 to the hydraulic cylinders 36 and 37 of the rear axle.

As will be described below, the steering arrange-55 ment shown in Figure 1 enables the wheels of the front axle41 of the vehicle with rubbertyresto be steered either, for road travel, mechanically from the steering gear 15 with hydraulic assistance by means of a steering rod 38 and track rod 39 (shown in Figure 60 2) or, for cross-country travel, purely hydraulicatly via the steering valve 28.

The operation is as follows:

For road-travel, the steering wheel 16 is connected viathe steering column 17, the V-drive 18 and the 65 propeller shaft 19 to the steering gear 15; the mechanical transmission of the movement of the steering wheel 16 to the front axle 41 is effected by means of the steering gear arm 40. The spool valves 13,22,30 and 32 are automatically switched into the 70 positions "a" shown in the drawing by an electro-switch 48 and the steering operaton is thus assisted hydraulicatly, in accordance with the movements of the steering wheel 16, via a spool valve arranged in the steering gear 15 in that the pressure oil supplied 75 by the hydraulic pump 10 is fed via the spool valve 22, which is in position "a", to the hydraulic cylinders 25 and 26, as described above.

During road-travel, the rear axle 42 is mechanically locked by a stop rod 43 and, as a result of the spool 80 valve 32 being in the position "a", the two hydraulic cylinders 36 and 37 of the rear axle 42 are also in a separate closed hydraulic circuit.

When, during road travel, the steering wheel 16 is not operated the pressure oil supplied by the 85 hydraulic pump 10 flows via the connection 15a and connection 15d of the steering gear 15 to the tank 44. When the steering wheel 16 is operated the pressure oil supplied by the hydraulic pump 10 flows from the -connection 15a of the steering gear 15 via either the 90 connection 15b or 15c (depending on the position of the steering gear spool valve) to the hydraulic cylinders 25 and 26 of the front axle 41.

In the case of purely hydraulic steering, the propeller shaft 19 is released from the connection to 95 the steering gear 15 and coupled mechanically with the steering valve 28.

If only the front axle 41 is to be steered, the spool valves 13,22 and 30 are automatically switched to the switching position "b"by theelectroswitch 48 100 whilethespool valve 32 remains in switching position "a". When the steering wheel 16 is operated the pressure oil supplied by the hydraulic pump 10 flows from the connection 28a of the steering valve 28 via the connection 28b or 28cto the hydraulic 105 cyli nders 25 and 26 of the front axle 41 as described above. If the steering wheel 16 is not operated the pressure oil flows from the hydraulic pump 10 via the rotary duct 45 to the steering valve 28, from the connection 28a to the connection 28d and via the 110 rotary duct 45 back to the tank 44.

In order to steer the front axle 41 and rear axle 42 in opposite directions and thus obtain the smallest possible degree of lock, the spool valve 32 is switched manually into switching position "c". The 115 spool valves 13,22 and 30 remain automatically in switching position "b".

In order to achieve steering in the same direction of the wheels of the front axle 41 and the rear axle 42, the spool valve 32 is switched manually into the 120 switching position "b". The spool valves 13,22 and 30 remain automatically in switching position "b".

If, however, it is required to change over to rear axle steering only (forthe purposes of travelling with the rear axle of the vehicle forwardly positioned) 125 then, by means of the electroswitch 48, the valve 30 is switched into the position "a" and the valve 32 into the position "b", with the valves 13 and 22 remaining in the position "b". The rear axle is now released for steering and the front axle is hydraulically locked 130 because the cylinders 25,26 are now in a separate

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closed hydraulic circuit. Moreover, despite the fact that it is the rear axle that is being steered, the vehicle can be steered in the customary manner, i.e. a left-hand turn is made by rotating the steering 5 wheel to the left and vice versa.

Further advantageous features of the arrangement described above are that the variable steering of the vehicle is achieved by means of a hydraulic circuit fed by a single pump and that, when the front and

10 rear axles are being steered purely hydraulically, there is a series connection of the hydraulic cylinders, so that the wheels of the front and rear axle run synchronously without mechanical coupling between the two axles.

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Claims

1. A steering arrangement for a vehicle, comprising an hydraulic circuit including an hydraulic pump

20 selectively connectible to supply fluid to first and second steering valve means, the first steering valve means being operable to control the supply of fluid from the pump to an hydraulic cylinder for one axle of the vehicle to assist mechanical steering of the

25 vehicle, and the second steering valve means being operable to control the supply of fluid from the pump to hydraulic cylinders of two axles of the vehicle to steer those axles, the second steering valve being selectively connectible to control the

30 supply of fluid to the hydraulic cylinders at least to steer either of those axles alone.

2. A steering arrangement as claimed in claim 1, in which the second steering valve means is also selectively connectible to control the supply of fluid

35 to the hydraulic cylinders to steer both of those axles together.

3. A steering arrangement as claimed in claim 2, in which the second steering valve means is connectible to two fluid control valves each associated with

40 a respective axle, the fluid control valves being interconnected and operable to connect the cylinders) for one axle in series with the cylinder(s) for the other axle.

4. A steering arrangement as claimed in claim 2

" 45 or claim 3, in which the second steering valve means is connectible to steer the two axles in opposite directions.

«

5. A steering arrangement as claimed in any one of claims 2 to 4, in which the second steering valve

50 means is connectible to steer the two axles in the same direction.

6. A steering arrangement as claimed in any one of the preceding claims, in which the first and second steering valve means are selectively connec-

55 tible to a steering device of the vehicle.

7. A steering arrangement as claimed in any one of the preceding claims, including a fluid control valve operable to control the selective connection of the hydraulic pump to the first and second steering

60 valve means.

8. A steering arrangement as claimed in any one of the preceding claims, in which the first steering valve means comprises a steering gear including a fluid control valve operable in accordance with

65 operation of a mechanical steering system of the vehicle.

9. A steering arrangement for a vehicle that has, according to choice, either hydraulically-assisted mechanical steering or purely hydraulic steering the 70 conversion of the hydraulically-assisted system into the system operating purely hydraulically being effected by means of the selective connection of a propeller shaft, which is connected to the steering wheel, to one of the two systems used for operating 75 the steering, in which a hydraulic pump acting on both systems and driven by the drive motor is connected via a line, a current-regulating and pressure relief valve and a line to a first spool valve from which:

80 (i) on the one hand, a line leads to a steering gear operated by the steering device via the propeller o shaft from which steering gear lines lead to a second spool valve that is connected via lines to the hydraulic cylinders of the front axle of the vehicle 85 and,

(ii) on the other hand, a line leads to a steering valve that is operated by means of the steering device and the propeller shaft, pressure oil flowing • from the steering valve either 90 (a) via a line to a third spool valve and via a line to the hydraulic cylinders of the front axle only or

(b) via a line to a fourth spool valve and via a line, the third spool valve and a line to the hydraulic cylinders of the front axle only or 95 (c) via a line to the third spool valve and via a line to the hydraulic cylinders of the front axle as well as via a line to the third spool valve and via a line, the fourth spool valve and a line to the hydraulic cylinders of the rear axle or 100 (d) via a line to the fourth spool valve and via a line to the hydraulic cylinders of the rear axle as well as via a line to the fourth spool valve and via a line, the third spool valve and a line to the hydraulic cylinders of the front axle or 105 (e) via a line to the third spool valve and, via a line, the fourth spool valve and a line to the hydraulic cylinders of the rear axle only or

(f) via a line to the fourth spool valve and via a line to the hydraulic cylinders of the rear axle only. 110

10. A steering arrangement as claimed in claim 9, including switch means actuable by the propeller shaft to operate the spool valves.

11. A steering arrangement for a vehicle, substantially as described herein with reference to, and 115 as illustrated by, the accompanying drawing.

Printed for Her Majesty's Stationery Office by Croydon Printing Company Limited, Croydon Surrey, 1980.

Published by the Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained.